Method for producing high temperature-resistant polyamide, high temperature-resistant polyamide and use thereof

ABSTRACT

The present invention provides a process for producing a high temperature resistant polyamide, the high temperature resistant polyamide and the use thereof. The process comprises: optionally concentrating a polyamide salt solution, and then conducting the following operations: heating and pressurizing to a pressure of P1, and maintaining the pressure, wherein the temperature of the system is T1 at the end of the pressure-maintenance; depressurizing to a pressure of P2, wherein the temperature of the system is T2 at the end of the depressurization; and evacuating, whereby a polyamide melt is obtained; wherein P1 is 0.8-4 MPa, T1 is 250-290° C., T1&lt;T2 and (T2−T1)/(P1−P2)=5-75. The process for producing a high temperature resistant polyamide according to the present invention is simple to operate and reduces energy consumption. The obtained high temperature resistant polyamide may be used as a raw material for such injection molded parts, molded articles, or fibers as high temperature resistant attachments for machines, automobiles, household appliances, toys, textiles, sporting goods, mobile phones, computers, laptops, GPS devices, or optical devices.

TECHNICAL FIELD

The invention relates to a process for producing a high temperatureresistant polyamide, the high temperature resistant polyamide and theuse thereof.

BACKGROUND ART

High temperature resistant polyamides generally refer to polyamideengineering plastics that can be used at, or above 150° C. for a longtime. High temperature resistant polyamides have good wear resistance,heat resistance, oil resistance and chemical resistance. They alsogreatly reduce water absorption and shrinkage of raw materials, and haveexcellent dimensional stability and excellent mechanical strength. Ascompared with aliphatic polyamides, semi-aromatic polyamides generallyhave excellent heat resistance. High temperature resistant polyamidesare increasingly used in the fields in which high heat resistance isdesired, such as automobile, construction, military, aerospaceindustries and the like. The types of high temperature resistantpolyamides that have been industrially produced mainly include PA46,PA6T, PA9T, etc. At the same time, novel high temperature resistantmaterials such as PA10T, PA4T, and PA12T also began to emerge.

At present, industrial production of semi-aromatic polyamides isconventionally conducted by a solution polycondensation process, whichgenerally comprises two steps: firstly, polymerizing in an autoclave toobtain a semi-aromatic polyamide prepolymer, and then carrying out meltpolycondensation, or solid state polymerization to increase themolecular weights, thereby obtaining a polyamide polymer. Therefore,such process is generally called a two-step process. For example,CN102372920A discloses a partially aromatic polyamide moldingcomposition and its use. Firstly, the formulation components of thepolyamide were placed into a 20 L autoclave together with a catalyst, aregulator and water. The reaction mixture was heated to a temperature of260° C. over a period of 50 to 80 minutes and maintained at a pressureof 32 bar for one hour. Subsequently, the pre-condensate was dischargedvia a nozzle. The pre-condensate was dried under a reduced pressure andpost-condensed in a double-screw extruder. Then the product was extrudedfrom a nozzle and pelletized.

Existing processes use water as solvent, and thus are cost-efficientlyand environmental-friendly. However, the produced prepolymers haverelatively low molecular weights, making it difficult to directly usethe same. A further melt polycondensation, or a solid phasepolymerization is needed to increase the molecular weights, which alsoprolongs the production cycle and increases the cost.

SUMMARY OF THE INVENTION

One embodiment according to the present invention provides a process forproducing a high temperature resistant polyamide, wherein the processcomprises:

optionally concentrating a polyamide salt solution, and then conductingthe following operations:

(1) heating and pressurizing to a pressure of P1, and maintaining thepressure, wherein the temperature of the system is T1 at the end of thepressure-maintenance;

(2) depressurizing to a pressure of P2, wherein the temperature of thesystem is T2 at the end of the depressurization; and

(3) evacuating, whereby a polyamide melt is obtained;

wherein P1 is 0.8-4 MPa, T1 is 250-290° C., T1<T2 and(T2−T1)/(P1−P2)=5-75.

One embodiment according to the present invention provides a hightemperature resistant polyamide, wherein the high temperature resistantpolyamide comprises at least a polyamide produced from Component (A)diamine and Component (B) diacid as raw materials, and the molar ratioof Component (A) to Component (B) is (0.5-5):1.

Component (A) diamine comprises:

any one of (a1) aliphatic linear, or branched diamines having 4 to 16carbon atoms; (a2) aromatic diamines, or cycloaliphatic diamines; or anycombination of two or more thereof; and/or

Component (B) diacid comprises:

any one of (b1) aliphatic diacids having 2 to 18 carbon atoms; (b2) abenzene ring-containing diacid having 8 carbon atoms, or more; or anycombination of two or more thereof.

One embodiment according to the present invention provides a hightemperature resistant polyamide, characterized in that the hightemperature resistant polyamide comprises at least a polyamide producedfrom a solution of Component (C) polyamide salt as a raw material.

One embodiment according to the present invention provides a hightemperature resistant polyamide, wherein a structural unit of the hightemperature resistant polyamide includes the following formula:

wherein n=4-16, and m=2-18.

In one embodiment, n is preferably 4-7.

In one embodiment, m is preferably 4-16.

The high temperature resistant polyamide has a melting point of 280-328°C., and preferably 286-328° C.

The high temperature resistant polyamide has a relative viscosity of1.80-2.70.

The high temperature resistant polyamide has a notched impact strengthof 5-12 KJ/cm², and preferably 6.5-10 KJ/cm².

The high temperature resistant polyamide has a tensile strength of95-140 MPa, preferably 105-134 MPa.

The high temperature resistant polyamide has a flexural strength of135-190 MPa, and preferably 155-183 MPa.

The high temperature resistant polyamide has a flexural modulus of3,500-4,400 MPa.

The high temperature resistant polyamide has a heat deflectiontemperature of 240-320° C., and preferably 260-300° C.

One embodiment according to the present invention provides a use of thehigh temperature resistant polyamide, wherein the high temperatureresistant polyamide is a raw material for injection molded parts, moldedarticles, or fibers.

The process for producing high temperature resistant polyamide has theadvantages that the process is simple and reduces energy consumptioncompared to existing polymerization processes. The correlation betweenpressure and temperature is utilized to solve the problem of high sampleresidue in the autoclave and overcome the difficulty in continuousmulti-batch production. The process is suitable for the production of ahigh temperature resistant polyamide with good product quality.

DETAILED DESCRIPTION OF THE DISCLOSURE

Typical embodiments embodying the features and advantages of the presentinvention will be described in detail in the following description. Itshould be understood that the present invention can have variousvariants in different embodiments without departing from the scope ofthe present invention. The description recited therein is substantivelyused for the purposes of illustration and should not be used to limitthe present invention.

One embodiment according to the present invention provides a process forproducing a high temperature resistant polyamide, wherein the processcomprises:

optionally concentrating a polyamide salt solution, and then conductingthe following operations:

(1) heating and pressurizing to a pressure of P1, and maintaining thepressure, wherein the temperature of the system is T1 at the end of thepressure-maintenance;

(2) depressurizing to a pressure of P2, wherein the temperature of thesystem is T2 at the end of the depressurization; and

(3) evacuating, whereby a polyamide melt is obtained.

Preferably, the process comprises the following steps:

optionally concentrating a polyamide salt solution having a massconcentration of 20 to 90 wt %, and then conducting the followingoperations:

(1) heating and pressurizing to a pressure of P1, and maintaining thepressure, wherein the temperature of the system is T1 at the end of thepressure-maintenance;

(2) depressurizing to a pressure of P2, wherein the temperature of thesystem is T2 at the end of the depressurization; and

(3) evacuating, whereby a polyamide melt is obtained.

In one embodiment, the process comprises the following steps:

mixing Component (A) diamine, Component (B) diacid and water to producea polyamide salt solution having a mass concentration of 20 to 90 wt %;optionally concentrating the polyamide salt solution, and thenconducting the following operations:

(1) heating and pressurizing to a pressure of P1, and maintaining thepressure, wherein the temperature of the system is T1 at the end of thepressure-maintenance;

(2) depressurizing to a pressure of P2, wherein the temperature of thesystem is T2 at the end of the depressurization; and

(3) evacuating, whereby a polyamide melt is obtained.

In one embodiment, when the polyamide salt solution has a massconcentration of 10 wt %, the pH value is 6.5 to 9.0, and preferably 7.6to 8.4, such as 7.2, 7.4, 7.6, 7.8, 8.0, 8.1, 8.2, 8.3, 8.5, or 8.7.Herein, the concentration in “the polyamide salt solution has a massconcentration of 10 wt %” can refer to the mass concentration of theunconcentrated polyamide salt solution as such, or the massconcentration obtained after sampling and diluting the concentrated, orunconcentrated polyamide salt solution. In one embodiment, the polyamidesalt solution has a mass concentration of 20 wt %, or more, andpreferably 20-90 wt %, such as 25 wt %, 30 wt %, 35 wt %, 40 wt %, 45 wt%, 48 wt %, 55 wt %, 57wt %, 60 wt %, 62 wt %, 65 wt %, 68 wt %, 70 wt%, 72 wt %, 75 wt %, 77 wt %, 80 wt %, or 85 wt %. Herein, the massconcentration of a polyamide salt solution can be the mass concentrationof the unconcentrated polyamide salt solution as such, or the massconcentration of the concentrated polyamide salt solution.

In one embodiment, the polyamide salt comprises a salt produced by thereaction of Component (A) diamine and Component (B) diacid. The molarratio of Component (A) to Component (B) is (0.5-5):1, preferably(0.6-3):1, more preferably (0.6-1.6):1, further more preferably(0.9-1.3):1, and still more preferably (1.01-1.3):1. The pH value of thepolyamide salt solution may be adjusted by controlling the molar ratioof the diamine to the diacid. For example, by making the diaminestoichiometrically excessive relative to the diacid, the pH of thepolyamide salt is made alkaline.

The polyamide salt solution comprises at least ions of Component (A)diamine and ions of Component (B) diacid.

In one embodiment, the polyamide salt solution comprises:

any one of (1) a solution obtained by mixing Component (A) diamine,Component (B) diacid and a solvent; (2) a solution obtained by mixingComponent (C) polyamide salt and a solvent; and (3) a solution obtainedby mixing Component (C) polyamide salt, Component (A) diamine and/orComponent (B) diacid and a solvent; or any combination of two or morethereof.

The solvent comprises, but is not limited to, water.

The salt produced by the reaction of diamine and diacid is polyamidesalt, which is also called “nylon salt”. Polyamide is obtained throughpolycondensation of a polyamide salt. During the polycondensation inStep (1) to Step (3), a carboxyl group and an amino group between thepolyamide salts are bonded and water is eliminated.

In one embodiment, the diamine, or the diacid may be produced by afermentation process, or an enzymatic conversion process.

In one embodiment, P1 is 0.8-4 MPa, and T1 is 250-290° C.

In one embodiment, P1 is 3-4 MPa.

In one embodiment, T1 is 275-290° C.

In some embodiments, P1 is, for example, 1 MPa, 1.2 MPa, 1.5 MPa, 1.8MPa, 2 MPa, 2.1 MPa, 2.2 MPa, 2.5 MPa, 3 MPa, 3.5 MPa, or 3.8 MPa.

In some embodiments, T1 is, for example, 255° C., 260° C., 262° C., 265°C., 268° C., 270° C., 272° C., 275° C., 277° C., 280° C., 283° C., or286° C.

In one embodiment, T1<T2, and (T2−T1)/(P1−P2)=5-75.

In one embodiment, T1<T2, and (T2−T1)/(P1−P2)=5-55.

In one embodiment, T1<T2, and (T2−T1)/(P1−P2)=10-45.

In one embodiment, T1<T2, and (T2−T1)/(P1−P2)=10-23.

In one embodiment, T1<T2, and (T2−T1)/(P1−P2)=10-16.

In one embodiment, (T2−T1)/(P1−P2) may be, for example, 10, 12, 14, 15,18, 20, 22, 25, 28, 30, 35, 40, 42, 46, 50, 55, 57, 63, 66, or 68.

(T2−T1) is the difference value between T2 (° C.) and T1 (° C.); (P1−P2)is the difference value between P1 (MPa) and P2 (MPa).

In one embodiment, Component (A) diamine comprises: any one of (a1)aliphatic linear, or branched diamines having 4 to 16 carbon atoms; (a2)aromatic diamines, or cycloaliphatic diamines; or any combination of twoor more thereof.

In one embodiment, Component (B) diacid comprises: any one of (b1)aliphatic diacids having 2 to 18 carbon atoms; (b2) a benzenering-containing diacid having 8, or more carbon atoms; or anycombination of two or more thereof.

In some embodiments, Component (a1) is aliphatic linear, or brancheddiamines having 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16 carbonatoms.

In some embodiments, the number of carbon atoms in Component (a2) is5-10, preferably 5-6, such as 5, 6, 7, 8, 9, or 10.

In some embodiments, the number of carbon atoms in Component (b1) may be2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18.

In one embodiment, the number of carbon atoms in Component (b2) may be8-12, and preferably 8-10.

In some embodiments, the number of carbon atoms in Component (b2) maybe, for example, 8, 9, 10, 11, or 12.

In one embodiment, Component (a1) comprises one, or more of butanediamine, pentane diamine, hexane diamine, heptane diamine, octanediamine, nonane diamine, decane diamine, undecane diamine, dodecanediamine, tridecane diamine, tetradecane diamine, pentadecane diamine,and hexadecane diamine.

In one embodiment, Component (a2) comprises one, or more of cyclopentanediamine, methyl cyclopentane diamine, cyclohexane diamine,p-phenylenediamine, o-phenylenediamine, and m-phenylenediamine.

In one embodiment, Component (b1) comprises one, or more of oxalic acid,malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid,suberic acid, azelaic acid, sebacic acid, undecanedioic acid,dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid,pentadecanedioic acid, hexadecanedioic acid, heptadecanedioic acid, andoctadecanedioic acid.

In one embodiment, Component (b2) comprises one, or more of terephthalicacid, isophthalic acid, and phthalic acid.

In one embodiment, the polyamide salt solution is a solution obtained bymixing at least Component (A) diamine, Component (B) diacid and asolvent.

In one embodiment, Component (A) diamine comprises: (a1) aliphaticlinear, or branched diamines having 4 to 16 carbon atoms; and Component(B) diacid comprises: (b1) aliphatic diacids having 2 to 18 carbonatoms, and (b2) one, or more of terephthalic acid, isophthalic acid, andphthalic acid.

In one embodiment, the molar ratio of Component (A) to Component (B) is(0.5-5):1, preferably (0.6-3):1, more preferably (0.6-1.6):1, furtherpreferably (0.9-1.3):1, and still more preferably (1.01-1.3):1, such as1:1, 1.1:1, 1.15:1, 1.2:1, 1.3:1, 1.5:1, 1.8:1, 2:1, 2.3:1, 2.5:1, 3:1,3.5:1, or 4:1.

In one embodiment, the molar ratio of Component (a1) to Component (b1)is (0.5-12):1, preferably (1-10):1, more preferably (1-8):1, furtherpreferably (2-5):1, and still more preferably (2.3-3.3):1, such as0.8:1, 1.2:1, 1.4:1, 1.5:1, 1.8:1, 2:1, 2.2:1, 2.5:1, 2.7:1, 3:1, 3.2:1,3.5:1, 4.5:1, 5:1, 6:1, 8:1, or 9:1.

In one embodiment, the molar ratio of Component (a1) to Component (b2)is (0.1-6):1, preferably (0.5-5):1, more preferably (0.5-4):1, furtherpreferably (1-4):1, more preferably (1-2):1, further preferably(1-1.7):1, and still more preferably (1.4-1.7):1, such as 0.2:1, 0.3:1,0.7:1, 1.0:1, 1.3:1, 1.5:1, 1.6:1, 1.8:1, 2:1, 2.3:1, 2.5:1, 2.6:1,2.8:1, 3:1, 3.5:1, 3.8:1, 4:1, or 4.6:1.

In one embodiment, the parameters such as the tensile strength, flexuralstrength, and/or flexural modulus of the polyamide product may beimproved by controlling the relationship between the components diaminesand diacids, especially the types, contents, and/or relative ratio.

In one embodiment, the content of Component (b2) is within thereasonable ranges as described above, and the parameters such as thetensile strength, flexural strength, flexural modulus of the polyamideproduct are improved.

In one embodiment, the flexibility of the polyamide product is improvedby introducing long-chain diacids/diamines.

In one embodiment, in Step (1), the pressure maintenance time is 1 to 4hours, and preferably 1.5 to 3 hours.

In one embodiment, in Step (1), the manner of pressure maintenance isdegassing to maintain pressure.

In one embodiment, during Step (2) of depressurizing to a pressure ofP2, the pressure P and the temperature T satisfy the followingconditions: when P is 0.4-0.65 times of P1, for example, when P is0.4-0.6 times of P1, or when P is 0.4-0.55 times of P1,T=(1.01-1.18)×T1; such as 1.095T1, 1.097T1, 1.101T1, 1.102T1, 1.11T1,1.115T1, 1.12T1, 1.13T1, 1.14T1, 1.145T1, 1.15T1, 1.16T1, or 1.17T1,wherein P2<P<P1, and T1<T<T2.

In one embodiment, during Step (2) of depressurizing to a pressure ofP2, the pressure P and the temperature T satisfy the followingconditions: when P is 0.4-0.65 times of P1, for example, when P is0.4-0.6 times of P1, or when P is 0.4-0.55 times of P1, T is(1.03-1.18)×T1, further preferably (1.04-1.18)×T1, more preferably(1.04-1.16)×T1, further preferably (1.04-1.15)×T1, more preferably(1.06-1.15)×T1, further more preferably (1.095-1.14)×T1, and still morepreferably (1.095-1.13)×T1, wherein P2<P<P1, and T1<T<T2.

In one embodiment, during Step (2) of depressurizing to a pressure ofP2, the pressure P and the temperature T satisfy the followingconditions: when P is 0.1-0.3 times of P1, for example, when P is0.12-0.3 times of P1, or when P is 0.14-0.3 times of P1, T is(1.132-1.26)×T1, such as 1.15T1, 1.17T1, 1.22T1, 1.23T1, 1.24T1, 1.25T1,or 1.27T1, wherein P2<P<P1, and T1<T<T2.

In one embodiment, during Step (2) of depressurizing to a pressure ofP2, the pressure P and the temperature T satisfy the followingconditions: when P is 0.1-0.3 times of P1, for example, when P is0.12-0.3 times of P1, or P is 0.14-0.3 times of P1, T is(1.132-1.20)×T1, further preferably (1.132-1.17)×T1, more preferably(1.132-1.16)×T1, and preferably (1.132-1.155))×T1, wherein P2<P<P1, andT1<T<T2.

In one embodiment, the yield of the process is improved by controllingthe course Step (2) of depressurizing.

In one embodiment, the relative viscosity of the obtained polyamideproduct is relatively higher by controlling the course of Step (2) ofdepressurizing.

In one embodiment, during the depressurization in Step (2), thetemperature of the system is kept increasing.

In one embodiment, the time period for the depressurization in Step (2)is 0.5 to 3 hours, and preferably 0.8 to 1.5 hours.

In one embodiment, T2 is 295-340° C., preferably 305-335° C., and morepreferably 325-335° C. For example, T2 is 300° C., 310° C., 315° C.,320° C., or 330° C.

In one embodiment, P2 is 0-0.05 MPa, and preferably 0-0.02 MPa. Forexample, P2 is 0.01 MPa, 0.02 MPa, 0.03 MPa, 0.035 MPa, or 0.04 MPa.

In one embodiment, P1>P2.

In one embodiment, during the polycondensation, in addition to the wateroriginally contained in the polyamide salt solution, the water existingin the system also comprises water produced during the polycondensation.

In one embodiment, steam is discharged during the polycondensation,which adjusts the reaction process, in particular reduces the pressureof the system.

In one embodiment, steam is discharged during Step (1) and Step (2) soas to reduce the pressure of the system.

In one embodiment, steam is discharged to the outside during Step (1),and the ratio of the discharged steam (mol) to the water content (mol)in the polyamide salt solution (abbreviated as dewatering ratio) is(60.6-93.9):100, preferably (75.4-90.9):100, more preferably(80-90.9):100, and still more preferably (87-90.9):100, such as 65:100,70:100, 72:100, 75:100, 78:100, 82:100, 84:100, 85:100, 86:100, 88:100,90:100, or 91:100.

In one embodiment, steam is discharged to the outside during Step (1),and the ratio of the discharged steam (mol) to the water content (mol)in the polyamide salt solution (abbreviated as dewatering ratio) is(60.6-93.9):100, preferably (75.4-93.9):100, more preferably(80-93.9):100, and still more preferably (87-93 .9): 100.

In one embodiment, steam is discharged during Step (2), and the ratio ofthe discharged steam (mol) to the water content (mol) in the polyamidesalt solution (abbreviated as dewatering ratio) is (93.9-118.2):100,preferably (93.9-114):100, preferably (98.7-113.9):100, such as 94:100,95:100, 96:100, 97:100, 98:100, 99:100, 100:100, 102:100, 103:100,105:100, 107:100, 110:100, or 112:100.

In one embodiment, steam is discharged during Step (2), and the ratio ofthe discharged steam (mol) to the water content (mol) in the polyamidesalt solution (abbreviated as dewatering ratio) is (93.9-118.2):100,further preferably (104-117):100, more preferably (110-117):100, andstill more preferably (110-114):100.

In one embodiment, prior to the reaction in Step (1), the polyamide saltsolution is concentrated, and the dewatering ratio in Step (1) and Step(2) is based on the concentrated polyamide salt solution.

In one embodiment, prior to the reaction in Step (1), the polyamide saltsolution is concentrated to a concentration of 50% to 85 wt %, morepreferably 55 to 70 wt %, and still more preferably 60 to 70 wt %, suchas 52 wt %, 55 wt %, 57 wt %, 60 wt %, 62 wt %, 65 wt %, 68 wt %, 70 wt%, 72 wt %, 75 wt %, 77 wt %, 80 wt % and 85 wt %.

In one embodiment, in Step (3), evacuation is conducted to a pressure of−0.09 to −0.005 MPa, further preferably −0.09 to −0.01 MPa, morepreferably −0.09 to −0.02 MPa, and still more preferably −0.065 to −0.04MPa.

In one embodiment, at the end of Step (3) of the evacuation, thetemperature of the system is 310-340° C., preferably 315-335° C., suchas 312° C., 318° C., 320° C., 325° C., 328° C., 330° C., or 333° C.

In one embodiment, the evacuation time in Step (3) is 1-40 min, andpreferably 4-20 min.

In one embodiment, the process further comprises Step (4): dischargingand pelletizing the polyamide melt, whereby a polyamide resin isobtained.

In one embodiment, the pelletization may be a water-coolingpelletization, and the temperature of the cooling water is 10-30° C.

In one embodiment, the polyamide salt solution further comprisesComponent (D) additive(s).

In one embodiment, Component (D) additive(s) are added at any stage ofStep (1) to Step (3).

In one embodiment, Component (D) comprises one, or more of antioxidants,defoamers, UV stabilizers, heat stabilizers, crystallizationaccelerators, free radical scavengers, lubricants, plasticizers, impactmodifiers, inorganic fillers, brighteners, dyes, flame retardants, andminerals.

In one embodiment, the molar quantity of Component (D) is (0.001-1)%,preferably (0.01-0.8)%, preferably (0.02-0.4)%, such as 0.03%, 0.05%,0.07%, 0.1%, 0.12%, 0.15%, 0.2%, 0.24%, 0.27%, 0.30%, 0.33%, 0.38%,0.45%, 0.5%, or 0.6% of the molar quantity of Component (A) and/orComponent (C).

In one embodiment, the heat stabilizer further comprises one, or more ofphosphoric acid, phosphorous acid, trimethyl phosphite, triphenylphosphite, trimethyl phosphate, triphenyl phosphate, sodiumhypophosphite, zinc hypophosphite, and potassium hypophosphite.

In one embodiment, the crystallization accelerator further comprises ametal salt of a long carbon chain carboxylic acid. The number of carbonatoms of the long carbon chain carboxylic acid is preferably 10-30, andthe metal preferably includes one, or more of calcium, magnesium, andzinc.

In one embodiment, the inorganic filler further comprises one, or moreof glass fibers, glass beads, carbon fibers, carbon black, and graphite.

In one embodiment, the mineral further comprises one ore more oftitanium dioxide, calcium carbonate, and barium sulfate.

In one embodiment, Component (D) additive(s) comprises at least anantioxidant.

In one embodiment, Component (D) additive(s) comprises at least adefoamer.

In one embodiment, Component (D) additive(s) comprises at least a heatstabilizer.

In one embodiment, Component (D) additive(s) comprises at least anantioxidant, a defoamer, and a heat stabilizer.

In one embodiment, the entire process for producing the high temperatureresistant polyamide is performed under an inert gas atmosphere.

In one embodiment, Step (1) and/or Step (2) and/or Step (3) and/or Step(4) are performed under an inert gas atmosphere.

The inert gas comprises nitrogen, argon, or helium.

One embodiment of the present invention provides a high temperatureresistant polyamide, comprising a polyamide produced from Component (A)diamine and Component (B) diacid as raw materials, and the molar ratioof Component (A) to Component (B) is (0.5-5):1.

In one embodiment, Component (A) diamine comprises:

any one of (a1) aliphatic linear, or branched diamines having 4 to 16carbon atoms; (a2) aromatic diamines, or cycloaliphatic diamines; or anycombination of two or more thereof.

In one embodiment, Component (B) diacid comprises:

any one of (b1) aliphatic diacids having 2 to 18 carbon atoms; (b2) abenzene ring-containing diacid having 8, or more carbon atoms; or anycombination of two or more thereof.

In one embodiment, the high temperature resistant polyamide comprises atleast a polyamide produced from a solution of Component (C) polyamidesalt as a raw material.

In one embodiment, the structural unit of the high temperature resistantpolyamide includes the following formula:

Wherein, n=4-16, preferably 4-10, and preferably 4-8, for example, n is4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16;

m=2-18, and preferably 4-16, for example, m is 2, 3, 4, 5, 6, 7, 8, 9,10, 11, 12, 13, 14, 15, or 16.

In one embodiment, a high temperature resistant polyamide is provided.The high temperature resistant polyamide has a melting point of 280-328°C., preferably 286-328° C., and preferably 293-320° C., such as 290,294, 298, 301, 304, 307, 309, 312, 315, 317, 321, or 325° C.

The high temperature resistant polyamide has a relative viscosity of1.80-2.70, and preferably 2.0-2.5, such as 1.85, 1.9, 1.95, 2.1, 2.2,2.3, 2.4, 2.55, 2.6, 2.67, or 2.7.

The high temperature resistant polyamide has a notched impact strengthof 5-12 KJ/cm², preferably 7.0-10 KJ/cm², and more preferably 6.5-10KJ/cm², such as 5.5, 6.5, 7.5, 8.0, 8.2, 8.5, 8.7, 9.3, 9.6, 9.8, 10.2,or 10.5 KJ/cm².

The high temperature resistant polyamide has a tensile strength of95-140 MPa, preferably 105-134 MPa, and more preferably 105-131 MPa,such as 100, 110, 112, 116, 119, 121, 125, 132, 135, or 138 MPa.

The high temperature resistant polyamide has a flexual strength of135-190 MPa, preferably 155-183 MPa, and more preferably 155-173 MPa,such as 140, 145, 150, 154, 157, 161, 164, 169, 172, 175, 178, 183, or185 MPa.

The high temperature resistant polyamide has a flexural modulus of3500-4400 MPa, and preferably 3700-4200 MPa, such as 3600, 3650, 3750,3800, 3850, 3890, 3920, 3950, 3995, 4050, 4130, 4200, or 4300 MPa.

The high temperature resistant polyamide has a heat deflectiontemperature of 240-320° C., preferably 270-310° C., and more preferably260-300° C., such as 249, 250, 251, 252, 253, 254, 255, 256, 257, 258 ,259, 260, 261, 262, 263, 264, 265, 266, 267, 268, 269, 270, 271, 272,273, 274, 275, 276, or 277° C.

In one embodiment, a use of the high temperature resistant polyamide isprovided, wherein the high temperature resistant polyamide is a rawmaterial for injection molded parts, molded articles, or fibers.

In one embodiment, the high temperature resistant polyamide is used as araw material for such injection molded parts, molded articles, or fibersas high temperature resistant attachments for machines, automobiles,household appliances, toys, textiles, sporting goods, mobile phones,computers, laptops, GPS devices, or optical devices.

The high temperature resistant polyamide and its preparation processaccording to one embodiment of the present invention will be furtherillustrated hereinafter in conjunction with specific Examples. Relevanttests as involved are as follows:

1) Flexural Strength and Flexural Modulus test: the test is conductedaccording to the standard ISO 178-2010 under a condition of 2 mm/min.The size of a sample bar is 10 mm*4 mm*80 mm.

2) Tensile Strength test: the test is conducted according to thestandard ISO 572-2-2012 under a condition of 50 mm/min.

3) Notched Impact Strength test: the notched impact strength test is acantilever beam notched impact test according to the measurementstandard ISO 180/1A under the test condition of 23° C.

4) Relative Viscosity: the relative viscosity is tested by usingconcentrated sulfuric acid and an Ubbelohde viscometer in the followingmanner: precisely weighing 0.25±0.0002 g dried polyamide resin chips,and adding 50 mL concentrated sulfuric acid (96 wt %) to dissolve thepolyamide resin chips, thereby obtaining a polyamide sample solution;and measuring and recording the flow time to of the concentratedsulfuric acid and the flow time of the polyamide sample solution in awater bath at a constant temperature of 25° C.

Relative viscosity is calculated according to the following equation:

relative viscosity=t/t ₀;

t represents the flow time of the polyamide sample solution; and torepresents the flow time of the solvent of concentrated sulfuric acid.

5) Heat Deflection Temperature (HDT): blending a polyamide produced inthe Examples with 30 wt % of glass fibers to obtain a glass fiberreinforced polyamide. Then the heat deflection temperature is testedaccording to the national standard GB/T 1634.2-2004, wherein the sampleis 120 mm*10 mm*4 mm in size (length*width*thickness), and the flexuralstress applied is 1.8 MPa.

6) Melting Point test: the test is performed on a differential scanningcalorimeter.

Unless otherwise specified, all the temperatures in the presentinvention are expressed in ° C., all the pressures are gauge pressures,and the pressures are expressed in MPa. Unless otherwise specified, theantioxidant H10 used in the Examples is BRUGGOLEN H10 antioxidant, andthe defoamer used in the Examples is Dow Corning Defoamer 3168.

EXAMPLE 1

The process for producing a high temperature resistant polyamidecomprised the following steps:

3838.73 mol of 1,5-pentanediamine, 1411.03 mol of adipic acid, 2423.04mol of terephthalic acid and water were mixed uniformly under a nitrogenatmosphere to produce a 50 wt % of polyamide salt solution. A sample wastaken from the polyamide salt solution. When the sample was diluted to aconcentration of 10 wt %, the pH value was 8.10. Sodium hypophosphite(120 ppm), antioxidant H10 (2000 ppm) and Dow Corning Defoamer 3168 (50ppm) were added to the polyamide salt solution and mixed uniformly.

The polyamide salt solution was heated to 138° C. so as to beconcentrated to a concentration of 65 wt %, and then subject to thefollowing steps:

Step (1): The polyamide salt solution was continued to heat andpressurized. The pressure within the reaction system was increased to3.5 MPa (P1), and the pressure is maintained by degassing. Thetemperature (T1) of the reaction system at the end of the pressuremaintenance was 279° C.

Step (2): While keeping the temperature increasing, the pressure beganto be reduced until the pressure within the reaction system dropped to 0MPa (P2, gauge pressure). At this time, the reaction system had atemperature (T2) of 330° C. During the depressurization, when thepressure (P) was 1.8 MPa, the system had a temperature (T) of 303° C.When the pressure (P) was 0.7 MPa, the system had a temperature (T) of319° C.

Step (3): The pressure was maintained at −0.06 MPa by evacuation. Theevacuation time was 15 minutes. The temperature of the system was 335°C. at the end of the evacuation, and a polyamide melt was obtained.

Step (4): The melt was discharged, and pelletized by cooling with waterto obtain a polyamide resin.

Wherein, the ratio of the discharged steam (mol) in Step (1) to thewater content (mol) in the concentrated polyamide salt solution (65 wt%) (abbreviated as dewatering ratio) was 90.2:100. The ratio of thedischarged steam (mol) in Step (2) to the water content (mol) in theconcentrated polyamide salt solution (65 wt %) (abbreviated asdewatering ratio) was 113.1:100.

EXAMPLE 2

The process for producing a high temperature resistant polyamidecomprised the following steps:

3875 mol of 1,5-pentanediamine, 1894.80 mol of adipic acid, 1975.02 molof terephthalic acid and water were mixed uniformly under a nitrogenatmosphere to produce a 50 wt % of polyamide salt solution. A sample wastaken from the polyamide salt solution. When the sample was diluted to aconcentration of 10 wt %, the pH value was 8.20. Sodium hypophosphite(120 ppm), antioxidant H10 (2000 ppm) and Dow Corning Defoamer 3168 (50ppm) were added to the polyamide salt solution and mixed uniformly.

The polyamide salt solution was heated to 130° C. so as to beconcentrated to a concentration of 68 wt %, and then subject to thefollowing steps:

Step (1): The polyamide salt solution was continued to heat andpressurized. The pressure within the reaction system was increased to2.5 MPa (P1), and the pressure was maintained by degassing. Thetemperature (T1) of the reaction system at the end of the pressuremaintenance was 267° C.

Step (2): While keeping the temperature increasing, the pressure beganto be reduced until the pressure within the reaction system dropped to 0MPa (P2, gauge pressure). At this time, the reaction system had atemperature (T2) of 315° C. During the depressurization, when thepressure (P) was 1.2 MPa, the system had a temperature (T) of 295° C.When the pressure (P) was 0.4 MPa, the system had a temperature (T) of308° C.

Step (3): The pressure was maintained at −0.04 MPa by evacuation. Theevacuation time was 10 minutes. The temperature of the system was 321°C. at the end of the evaluation, and a polyamide melt was obtained.

Step (4): The melt was discharged, and pelletized by cooling with waterto obtain a polyamide resin.

Wherein, the ratio of the discharged steam (mol) in Step (1) to thewater content (mol) in the concentrated polyamide salt solution (68 wt%) (abbreviated as dewatering ratio) was 83.3:100. The ratio of thedischarged steam (mol) in Step (2) to the water content (mol) in theconcentrated polyamide salt solution (68 wt %) (abbreviated asdewatering ratio) was 106.9:100.

EXAMPLE 3

The process for producing a high temperature resistant polyamidecomprised the following steps:

3913.92 mol of 1,5-pentanediamine, 2418.56 mol of adipic acid, 1490.82mol of terephthalic acid and water were mixed uniformly under a nitrogenatmosphere to produce a 50 wt % of polyamide salt solution. A sample wastaken from the polyamide salt solution. When the sample was diluted to aconcentration of 10 wt %, the pH value was 8.20. Sodium hypophosphite(120 ppm), antioxidant H10 (2000 ppm) and Dow Corning Defoamer 3168 (50ppm) were added to the polyamide salt solution and mixed uniformly.

The polyamide salt solution was heated to 122° C. so as to beconcentrated to a concentration of 62 wt %, and then subject to thefollowing steps:

Step (1): The polyamide salt solution was continued to heat andpressurized. The pressure within the reaction system was increased to1.4 MPa (P1), and the pressure was maintained by degassing. Thetemperature (T1) of the reaction system at the end of the pressuremaintenance was 255° C.

Step (2): While keeping the temperature increasing, the pressure beganto be reduced until the pressure within the reaction system dropped to 0MPa (P2, gauge pressure). At this time, the reaction system had atemperature (T2) of 299° C. During the depressurization, when thepressure (P) was 0.7 MPa, the system had a temperature (T) of 287° C.When the pressure (P) was 0.2 MPa, the system had a temperature (T) of298° C.

Step (3): The pressure was maintained at −0.02 MPa by evacuation. Theevacuation time was 5 minutes. The temperature of the system was 313° C.at the end of the evaluation, and a polyamide melt was obtained.

Step (4): The melt was discharged, and pelletized by cooling with waterto obtain a polyamide resin.

Wherein, the ratio of the discharged steam (mol) in Step (1) to thewater content (mol) in the concentrated polyamide salt solution (62 wt%) (abbreviated as dewatering ratio) was 77.6:100. The ratio of thedischarged steam (mol) in Step (2) to the water content (mol) in theconcentrated polyamide salt solution (62 wt %) (abbreviated asdewatering ratio) was 99.8:100.

EXAMPLE 4

The process for producing a high temperature resistant polyamidecomprised the following steps:

2977.99 mol of decane diamine, 625 mol of adipic acid, 2351.05 mol ofterephthalic acid and water were mixed uniformly under a nitrogenatmosphere to produce a 50 wt % of polyamide salt solution. A sample wastaken from the polyamide salt solution. When the sample was diluted to aconcentration of 10 wt %, the pH value was 8.20. Sodium hypophosphite(120 ppm), antioxidant H10 (2000 ppm) and Dow Corning Defoamer 3168 (50ppm) were added to the polyamide salt solution and mixed uniformly.

The polyamide salt solution was heated to 130° C. so as to beconcentrated to a concentration of 65 wt %, and then subject to thefollowing steps:

Step (1): The polyamide salt solution was continued to heat andpressurized. The pressure within the reaction system was increased to2.5 MPa (P1), and the pressure was maintained by degassing. Thetemperature (T1) of the reaction system at the end of the pressuremaintenance was 270° C.

Step (2): While keeping the temperature increasing, the pressure beganto be reduced until the pressure within the reaction system dropped to 0MPa (P2, gauge pressure). At this time, the reaction system had atemperature (T2) of 320° C. During the depressurization, when thepressure (P) was 1.1 MPa, the system had a temperature (T) of 305° C.When the pressure (P) was 0.8 MPa, the system had a temperature (T) of318° C.

Step (3): The pressure was maintained at −0.04 MPa by evacuation. Theevacuation time was 10 minutes. The temperature of the system was 320°C. at the end of the evaluation, and a polyamide melt was obtained.

Step (4): The melt was discharged, and pelletized by cooling with waterto obtain a polyamide resin.

Wherein, the ratio of the discharged steam (mol) in Step (1) to thewater content (mol) in the concentrated polyamide salt solution (65 wt%) (abbreviated as dewatering ratio) was 83.1:100. The ratio of thedischarged steam (mol) in Step (2) to the water content (mol) in theconcentrated polyamide salt solution (65 wt %) (abbreviated asdewatering ratio) was 106.9:100.

EXAMPLE 5

The process for producing a high temperature resistant polyamidecomprised the following steps:

3587.55 mol of 1,5-pentanediamine, 602.39 mol of dodecanedioic acid,2982.72 mol of terephthalic acid and water were mixed uniformly under anitrogen atmosphere to produce a 50 wt % of polyamide salt solution. Asample was taken from the polyamide salt solution. When the sample wasdiluted to a concentration of 10 wt %, the pH value was 8.20. SodiumHypophosphite (120 ppm), antioxidant H10 (2000 ppm), and Dow CorningDefoamer 3168 (50 ppm) were added to the polyamide salt solution andmixed uniformly.

The polyamide salt solution was heated to 130° C. so as to beconcentrated to a concentration of 65 wt %, and then subject to thefollowing steps:

Step (1): The polyamide salt solution was continued to heat andpressurized. The pressure within the reaction system was increased to2.5 MPa (P1), and the pressure was maintained by degassing. Thetemperature (T1) of the reaction system at the end of the pressuremaintenance was 275° C.

Step (2): While keeping the temperature increasing, the pressure beganto be reduced until the pressure within the reaction system dropped to 0MPa (P2, gauge pressure). At this time, the reaction system had atemperature (T2) of 315° C. During the depressurization, when thepressure (P) was 1.3 MPa, the system had a temperature (T) of 300° C.When the pressure (P) was 0.7 MPa, the system had a temperature (T) of314° C.

Step (3): The pressure was maintained at −0.04 MPa by evacuation. Theevacuation time was 10 minutes. The temperature of the system was 318°C. at the end of the evaluation, and a polyamide melt was obtained.

Step (4): The melt was discharged, and pelletized by cooling with waterto obtain a polyamide resin.

Wherein, the ratio of the discharged steam (mol) in Step (1) to thewater content (mol) in the concentrated polyamide salt solution (65 wt%) (abbreviated as dewatering ratio) was 81.0:100. The ratio of thedischarged steam (mol) in Step (2) to the water content (mol) in theconcentrated polyamide salt solution (65 wt %) (abbreviated asdewatering ratio) was 110.5:100.

EXAMPLE 6

The steps and conditions for preparing the high temperature resistantpolyamide are the same as those in Example 1, except that in Step (2),while keeping the temperature increasing, the pressure began to bereduced until the pressure within the reaction system dropped to 0 MPa(P2, gauge pressure); at this time, the reaction system had atemperature (T2) of 330° C.; during the depressurization, when thepressure (P) was 1.5 MPa, the system had a temperature (T) of 283° C.,and when the pressure (P) was 0.7 MPa, the system had a temperature (T)of 319° C.

EXAMPLE 7

The steps and conditions for preparing the high temperature resistantpolyamide are the same as those in Example 1, except that in Step (2),while keeping the temperature increasing, the pressure began to bereduced until the pressure within the reaction system dropped to 0 MPa(P2, gauge pressure); at this time, the reaction system had atemperature (T2) of 330° C.; during the depressurization, when thepressure (P) was 1.8 MPa, the system had a temperature (T) of 303° C.;and when the pressure (P) was 0.6 MPa, the system had a temperature (T)of 330° C.

EXAMPLE 8

The steps and conditions for preparing the high temperature resistantpolyamide are the same as those in Example 1, except that in Step (2),while keeping the temperature increasing, the pressure began to bereduced until the pressure within the reaction system dropped to 0 MPa(P2, gauge pressure); at this time, the reaction system had atemperature (T2) of 330° C.; during the depressurization, when thepressure (P) was 1.5 MPa, the system had a temperature (T) of 283° C.;and when the pressure (P) was 0.6 MPa, the system had a temperature (T)of 330° C.

EXAMPLE 9

The steps and conditions for preparing the high temperature resistantpolyamide are the same as those in Example 1, except that the ratio ofthe discharged steam (mol) in Step (1) to the water content (mol) in theconcentrated polyamide salt solution (65 wt %) (abbreviated asdewatering ratio) was 69.5:100; and the ratio of the discharged steam(mol) in Step (2) to the water content (mol) in the concentratedpolyamide salt solution (65 wt %) (abbreviated as dewatering ratio) was113.1:100.

EXAMPLE 10

The steps and conditions for preparing the high temperature resistantpolyamide are the same as those in Example 1, except that the ratio ofthe discharged steam (mol) in Step (1) to the water content (mol) in theconcentrated polyamide salt solution (65 wt %) (abbreviated asdewatering ratio) was 70.2:100; and the ratio of the discharged steam(mol) in Step (2) to the water content (mol) in the concentratedpolyamide salt solution (65 wt %) (abbreviated as dewatering ratio) was116.7:100.

EXAMPLE 11

The steps and conditions for preparing the high temperature resistantpolyamide are the same as those in Example 4, except that in Step (2),while keeping the temperature increasing, the pressure began to bereduced until the pressure within the reaction system dropped to 0 MPa(P2, gauge pressure); at this time, the reaction system had atemperature (T2) of 330° C.; during the depressurization, when thepressure (P) was 1.5 MPa, the system had a temperature (T) of 275° C.;and when the pressure (P) was 0.7 MPa, the system had a temperature (T)of 319° C.

the ratio of the discharged steam (mol) in Step (1) to the water content(mol) in the concentrated polyamide salt solution (65 wt %) (abbreviatedas dewatering ratio) was 71.4:100; and the ratio of the discharged steam(mol) in Step (2) to the water content (mol) in the concentratedpolyamide salt solution (65 wt %) (abbreviated as dewatering ratio) was113.1:100.

The test results for the polyamide resins obtained in the aforementionedExamples were shown in Table 1.

TABLE 1 Melting Tensile Flexural Flexural Notched Yield Point RelativeStrength Strength Modulus Impact Strength HDT (%) (° C.) Viscosity (MPa)(MPa) (MPa) (KJ/m²) (° C.) Example 1 98 318 2.43 130 173 3996 9.1 277Example 2 98 296 2.42 128 171 3960 9.2 265 Example 3 98 281 2.42 124 1683911 9.4 249 Example 4 97 305 2.42 123 166 3915 9.8 268 Example 5 98 3002.41 120 162 3886 9.6 266 Example 6 96 318 2.38 129 172 3993 9.1 277Example 7 95 318 2.37 129 172 3991 9.1 277 Example 8 93 318 2.38 128 1713990 9.1 277 Example 9 95 318 2.39 129 172 3989 9.1 277 Example 10 92318 2.36 129 172 3982 9.0 277 Example 11 92 305 2.27 122 165 3910 9.7268

Unless specifically limited, the terms used in the present inventionhave the meanings commonly understood by those skilled in the art.

The embodiments described in the present invention are for illustrativepurposes only, and are not intended to limit the protection scope of thepresent invention. Those skilled in the art can make varioussubstitutions, modifications and improvements within the scope of thepresent invention. Therefore, the present invention is not limited tothe above-mentioned embodiments but only defined by the claims.

What is claimed is:
 1. A process for producing a high temperatureresistant polyamide, characterized in that the process comprises:optionally concentrating a polyamide salt solution, and then conductingthe following operations: (1) heating and pressurizing to a pressure ofP1, and maintaining the pressure, wherein the temperature of the systemis T1 at the end of the pressure-maintenance; (2) depressurizing to apressure of P2, wherein the temperature of the system is T2 at the endof the depressurization; and (3) evacuating, whereby a polyamide melt isobtained; wherein P1 is 0.8-4 MPa, T1 is 250-290° C., T1<T2 and(T2−T1)/(P1−P2)=5-75.
 2. The process for producing a high temperatureresistant polyamide according to claim 1, characterized in that: themass concentration of the polyamide salt solution is 20 wt %, or more,and preferably 20 to 90 wt %; and/or prior to Step (1), the pH value is6.5-9.0 when the concentration of the polyamide salt solution is 10 wt%.
 3. The process for producing a high temperature resistant polyamideaccording to claim 1, characterized in that: the polyamide saltcomprises a salt produced by the reaction of Component (A) diamine andComponent (B) diacid; and/or the polyamide salt solution comprises atleast ions of Component (A) diamine and ions of Component (B) diacid;and/or the polyamide salt solution comprises: any one of (1) a solutionobtained by mixing Component (A) diamine, Component (B) diacid and asolvent; (2) a solution obtained by mixing Component (C) polyamide saltand a solvent; and (3) a solution obtained by mixing Component (C)polyamide salt, Component (A) diamine and/or Component (B) diacid and asolvent; or any combination of two or more thereof.
 4. The process forproducing a high temperature resistant polyamide according to claim 3,characterized in that Component (A) diamine comprises: any one of (a1)aliphatic linear, or branched diamines having 4 to 16 carbon atoms; (a2)aromatic diamines, or cycloaliphatic diamines; or any combination of twoor more thereof; and/or Component (B) diacid comprises: any one of (b1)aliphatic diacids having 2 to 18 carbon atoms; (b2) a benzenering-containing diacid having 8, or more carbon atoms; or anycombination of two or more thereof.
 5. The process for producing a hightemperature resistant polyamide according to claim 4, characterized inthat: Component (a1) comprises one, or more of butane diamine, pentanediamine, hexane diamine, heptane diamine, octane diamine, nonanediamine, decane diamine, undecane diamine, dodecane diamine, tridecanediamine, tetradecane diamine, pentadecane diamine, and hexadecanediamine; and/or Component (a2) comprises one, or more of cyclopentanediamine, methyl cyclopentane diamine, cyclohexane diamine,p-phenylenediamine, o-phenylenediamine, and m-phenylenediamine; and/orComponent (b1) comprises one, or more of oxalic acid, malonic acid,succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid,azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid,tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid,hexadecanedioic acid, heptadecanedioic acid, and octadecanedioic acid;and/or Component (b2) comprises one, or more of terephthalic acid,isophthalic acid, and phthalic acid.
 6. The process for producing a hightemperature resistant polyamide according to claim 4, characterized inthat: the molar ratio of Component (A) to Component (B) is (0.5-5):1;and/or the molar ratio of Component (a1) to Component (bl) is(0.5-12):1; and/or the molar ratio of Component (a1) to Component (b2)is (0.1-6):1.
 7. The process for producing a high temperature resistantpolyamide according to claim 1, characterized in that: during Step (2)of depressurizing to a pressure of P2, the pressure P and thetemperature T satisfy the following conditions: when P is 0.4-0.65 timesof P1, T=(1.01-1.18)×T1; and/or during Step (2) of depressurizing to apressure of P2, the pressure P and the temperature T satisfy thefollowing conditions: when P is 0.1-0.3 times of P1, T=(1.132-1.26)×T1;wherein P2<P<P1, and T1<T<T2.
 8. The process for producing a hightemperature resistant polyamide according to claim 1, characterized inthat: in Step (1), steam is discharged to the outside, and the ratio ofthe discharged steam (mol) to the water content (mol) in the polyamidesalt solution is (60.6-93.9):100.
 9. The process for producing a hightemperature resistant polyamide according to claim 1, characterized inthat: in Step (2), steam is discharged to the outside, and the ratio ofthe discharged steam (mol) to the water content (mol) in the polyamidesalt solution is (93.9-118.2):100.
 10. The process for producing a hightemperature resistant polyamide according to claim 1, characterized inthat: prior to Step (1), the polyamide salt solution is concentrated toa concentration of 50-85 wt %; and/or adding Component (D) additive(s)in any stage of Step (1) to Step (3); and/or T2 is 295-340° C., andT1<T2; and/or P2 is 0-0.05 MPa, and P1>P2; and/or in Step (3),evacuating to a pressure of −0.09 to −0.005 MPa; and/or in Step (3), thetemperature of the system is 310-340° C. at the end of the evacuation;and/or the process further comprises Step (4): discharging andpelletizing the polyamide melt, whereby a polyamide resin is obtained.11. The process for producing a high temperature resistant polyamideaccording to claim 3, characterized in that the polyamide salt solutionfurther comprises Component (D) additive(s); Component (D) comprisesone, or more of antioxidants, defoamers, UV stabilizers, heatstabilizers, crystallization accelerators, free radical scavengers,lubricants, plasticizers, impact modifiers, inorganic fillers,brighteners, dyes, flame retardants, and minerals; and/or the molarquantity of Component (D) is 0.001% to 1% and preferably 0.01% to 0.8%of the molar quantity of Component (A) and/or Component (C).
 12. A hightemperature resistant polyamide, characterized in that the hightemperature resistant polyamide comprises at least a polyamide producedfrom Component (A) diamine and Component (B) diacid as raw materials,the molar ratio of Component (A) to Component (B) is (0.5-5):1, andpreferably (1.01-1.3):1; and/or Component (A) diamine comprises: any oneof (a1) aliphatic linear, or branched diamines having 4 to 16 carbonatoms; (a2) aromatic diamines, or cycloaliphatic diamines; or anycombination of two or more thereof; and/or Component (B) diacidcomprises: any one of (b1) aliphatic diacids having 2 to 18 carbonatoms; (b2) a benzene ring-containing diacid having 8 carbon atoms, ormore; or any combination of two or more thereof.
 13. (canceled)
 14. Ahigh temperature resistant polyamide, characterized in that a structuralunit of the high temperature resistant polyamide includes the followingformula:

wherein n=4-16, and m=2-18.
 15. The high temperature resistant polyamideaccording to claim 12, characterized in that: the high temperatureresistant polyamide has a melting point of 280-328° C., and preferably286-328° C.; and/or the high temperature resistant polyamide has arelative viscosity of 1.80-2.70; and/or the high temperature resistantpolyamide has a notched impact strength of 5-12 KJ/cm², and preferably6.5-10 KJ/cm²; and/or the high temperature resistant polyamide has atensile strength of 95-140 MPa, preferably 105-134 MPa; and/or the hightemperature resistant polyamide has a flexural strength of 135-190 MPa,and preferably 155-183 MPa; and/or the high temperature resistantpolyamide has a flexural modulus of 3,500-4,400 MPa; and/or the hightemperature resistant polyamide has a heat deflection temperature of240-320° C., and preferably 260-300° C.
 16. The high temperatureresistant polyamide produced by a process according to claim 1,characterized in that the high temperature resistant polyamide is usedas a raw material for injection molded parts, molded articles, orfibers; and preferably, the high temperature resistant polyamide is usedas a raw material for such injection molded parts, molded articles, orfibers as high temperature resistant attachments for machines,automobiles, household appliances, toys, textiles, sporting goods,mobile phones, computers, laptops, GPS devices, or optical devices.